Generally, various kinds of apparatuses and methods have been widely used to generate a multi-channel media signal by using spatial information for the multi-channel media signal and a downmix signal, in which the downmix signal is generated by downmixing the multi-channel media signal into mono or stereo signal.
However, the above methods and apparatuses are not usable in environments unsuitable for generating a multi-channel signal. For instance, they are not usable for a device capable of generating only a stereo signal. In other words, there exists no method or apparatus for generating a surround signal, in which the surround signal has multi-channel features in the environment incapable of generating a multi-channel signal by using spatial information of the multi-channel signal.
So, since there exists no method or apparatus for generating a surround signal in a device capable of generating only a mono or stereo signal, it is difficult to process the media signal efficiently.